Method and device for determining equivalent heat conductivity coefficient of secondary transposition Litz line

Abstract

The invention provides a method and a device for determining an equivalent heat conductivity coefficient of a secondary transposition Litz line. The method comprises the following steps: constructing a first parallel thermal resistance model along the length direction, a second series thermal resistance model and a second parallel thermal resistance model along the width direction, and a third series thermal resistance model and a third parallel thermal resistance model along the thickness direction of the secondary transposition Litz line; determining a first equivalent heat conductivity coefficient of the secondary transposition Litz line along the length direction based on a first parallel thermal resistance model; determining a second equivalent heat conductivity coefficient of the secondary transposition Litz line along the width direction based on the second series thermal resistance model and the second parallel thermal resistance model; and determining a third equivalent heat conductivity coefficient of the secondary transposition Litz line along the width direction based on the third series thermal resistance model and the third parallel thermal resistance model. According to the method, the common influence of two conditions of series heat diffusion and parallel heat diffusion on the equivalent heat conductivity coefficient is considered, and the accuracy of the determined equivalent heat conductivity coefficient is improved.

Description

Technical Field

[0001] The invention relates to the technical field of temperature field analysis, and in particular to a method and a device for determining an equivalent thermal conductivity coefficient of a secondary transposed Litz line. Background Art

[0002] For some special motors (high-speed motors and high magnetic load motors, etc.) or power transformers, the coils are wound with Litz transposed wires, which can significantly reduce the coil circulating current and eddy current losses, and improve the operating reliability and life. When performing thermal analysis on these special motors, it is usually necessary to predict their thermal load capacity and maximum temperature rise, which requires accurate input of material thermal parameters, so the evaluation of the thermal parameters of the litz transposed wire is particularly important.

[0003] Many methods are used to estimate the equivalent thermal conductivity of litz-transposed conductors, including experimental determination, simulation analysis, and equivalent analysis methods. The equivalent analysis method can usually evaluate the thermal conductivity of litz wires in a time- and resource-saving manner. The disadvantage is that the accuracy of the analysis method in evaluating the equivalent thermal conductivity of litz-transposed conductors depends on the simplified model. Most of the existing physical models are simplified to simple parallel models or series models, while the heat flow in litz-transposed conductors has two situations: series heat diffusion and parallel heat diffusion between different materials. Therefore, the equivalent parameters derived using simple parallel models or series models cannot reflect the actual structure, affecting the accuracy of the simulation analysis results.

[0004] Therefore, it is urgent to provide a method and device for determining the equivalent thermal conductivity of a secondary transposed Litz wire, taking into account the joint influence of series and parallel conditions on the thermal conductivity, and improving the accuracy of thermal simulation of the secondary transposed Litz wire. Summary of the invention

[0005] In view of this, it is necessary to provide a method and device for determining the equivalent thermal conductivity of a secondary transposed Litz line to solve the technical problem in the prior art that only a single series or parallel model is considered to derive the equivalent thermal conductivity, resulting in inaccurate equivalence of the thermal conductivity of the secondary transposed Litz line.

[0006] On the one hand, in order to solve the above technical problems, the present invention provides a method for determining the equivalent thermal conductivity of a secondary transposed Litz line, comprising: Constructing a first parallel thermal resistance model along the length direction, a second series thermal resistance model and a second parallel thermal resistance model along the width direction, and a third series thermal resistance model and a third parallel thermal resistance model along the thickness direction of the secondary transposed Litz line; Determine a first equivalent thermal conductivity of the secondary transposed Litz line along the length direction based on the first parallel thermal resistance model; Determine the second series thermal conductivity and the second parallel thermal conductivity of the secondary transposed Litz line along the width direction based on the second series thermal resistance model and the second parallel thermal resistance model, and use the weighted sum of the second series thermal conductivity and the second parallel thermal conductivity as the second equivalent thermal conductivity of the secondary transposed Litz line along the width direction; A third series thermal conductivity and a third parallel thermal conductivity of the secondary transposition Litz line along the thickness direction are determined based on the third series thermal resistance model and the third parallel thermal resistance model, respectively, and a weighted sum of the third series thermal conductivity and the third parallel thermal conductivity is used as the third equivalent thermal conductivity of the secondary transposition Litz line along the thickness direction.

[0007] In a possible implementation, the preparation process of the secondary transposed Litz wire is: Treating the round copper wire with an insulating paint film to obtain an enameled round copper wire; Transposing a plurality of enameled round copper wires, performing vacuum pressure impregnation on the transposed plurality of enameled round copper wires to obtain a primary transposed Litz wire, and wrapping a first polyimide film around the primary transposed Litz wire; The first transposed Litz wire wrapped with the first polyimide film is subjected to a second transposition to obtain a second transposed Litz wire, a second polyimide film is wrapped around the second transposed Litz wire, and the second transposed Litz wire wrapped with the second polyimide film is subjected to vacuum pressure impregnation.

[0008] In a possible implementation, the second series thermal resistance model includes the enameled copper round wire series thermal resistance model of the enameled copper round wire, the first transposition series thermal resistance model of the first transposition Litz wire, and the second transposition series thermal resistance model of the transposition Litz wire; then determining the second series thermal conductivity of the second transposition Litz wire along the width direction based on the second series thermal resistance model includes: Determine the enameled series equivalent thermal resistance of the enameled round copper wire based on the enameled round copper wire series thermal resistance model, and determine the enameled round copper wire equivalent series thermal conductivity based on the enameled series equivalent thermal resistance and the size parameters of the enameled round copper wire; Determine the first transposition series equivalent thermal resistance of the first transposition Litz wire based on the first transposition series thermal resistance model and the enameled series equivalent thermal resistance, and determine the first transposition equivalent series thermal conductivity based on the first transposition series equivalent thermal resistance and the size parameters of the first transposition Litz wire; The secondary transposition series equivalent thermal resistance of the secondary transposition Litz line is determined based on the secondary transposition series thermal resistance model and the primary transposition series equivalent thermal resistance, and the second series thermal conductivity is determined based on the secondary transposition series equivalent thermal resistance and the size parameters of the secondary transposition Litz line.

[0009] In a possible implementation, the second series thermal conductivity is:

[0010] In the formula, is the second series thermal conductivity; is the equivalent thermal resistance of the secondary transposition series connection; w is the width of a transposed Litz line; b is the thickness of the Litz line of a transposition; t 3 is the double-sided thickness of the first polyimide film; t 4 is the bilateral thickness of the resin layer in the secondary transposition Litz line; t 5 is the thickness of the second polyimide film; dl It is the length of a single enameled round copper wire along the length direction.

[0011] In a possible implementation, the second parallel thermal resistance model includes the enameled copper round wire parallel thermal resistance model of the enameled copper round wire, the first transposition parallel thermal resistance model of the first transposition Litz wire, and the second transposition parallel thermal resistance model of the transposition Litz wire; then determining the second parallel thermal conductivity of the second transposition Litz wire along the width direction based on the second parallel thermal resistance model includes: Determine the enameled parallel equivalent thermal resistance of the enameled round copper wire based on the enameled round copper wire parallel thermal resistance model, and determine the enameled round copper wire equivalent parallel thermal conductivity based on the parallel equivalent thermal resistance and the size parameters of the enameled round copper wire; Determine the first-transposition parallel equivalent thermal resistance of the first-transposition Litz wire based on the first-transposition parallel thermal resistance model and the equivalent parallel thermal conductivity of the enameled copper round wire, and determine the first-transposition equivalent parallel thermal conductivity based on the first-transposition parallel equivalent thermal resistance and the size parameters of the first-transposition Litz wire; The secondary transposition parallel equivalent thermal resistance of the secondary transposition Litz line is determined based on the secondary transposition parallel thermal resistance model and the primary transposition series equivalent thermal resistance, and the second parallel thermal conductivity is determined based on the secondary transposition parallel equivalent thermal resistance and the size parameters of the secondary transposition Litz line.

[0012] In a possible implementation, the second parallel thermal conductivity is:

[0013] In the formula, is the second parallel thermal conductivity; is the secondary transposition parallel equivalent thermal resistance; w is the width of a transposed Litz line; b is the thickness of the Litz line of a transposition;t 3 is the double-sided thickness of the first polyimide film; t 4 is the bilateral thickness of the resin layer in the secondary transposition Litz line; t 5 is the thickness of the second polyimide film; dl It is the length of a single enameled round copper wire along the length direction.

[0014] In a possible implementation, the method further includes: Obtaining the diameter of the round copper wire and the film thickness of the insulating paint film; Determining a volume fraction of the copper round wire based on the diameter and the paint film thickness, and determining a first weight of the second series thermal conductivity and a second weight of the third series thermal conductivity based on the volume fraction; The second equivalent thermal conductivity and the third equivalent thermal conductivity are determined based on the first weight, the second weight, the second series thermal conductivity, the second parallel thermal conductivity, the third series thermal conductivity, and the third parallel thermal conductivity.

[0015] In a possible implementation, the second equivalent thermal conductivity is:

[0016]

[0017] In the formula, is the second equivalent thermal conductivity; is the first weight; V m is the volume fraction of copper round wire.

[0018] In a possible implementation, the third equivalent thermal conductivity is:

[0019]

[0020] In the formula, is the second equivalent thermal conductivity; is the second weight; V m is the volume fraction of copper round wire.

[0021] On the other hand, the present invention also provides a device for determining the equivalent thermal conductivity of a secondary transposed Litz line, comprising: A series-parallel thermal resistance model construction unit, used to construct a first parallel thermal resistance model along the length direction, a second series thermal resistance model and a second parallel thermal resistance model along the width direction, and a third series thermal resistance model and a third parallel thermal resistance model along the thickness direction of the secondary transposed Litz line; A first equivalent thermal conductivity determination unit, configured to determine a first equivalent thermal conductivity of the secondary transposed Litz line along a length direction based on the first parallel thermal resistance model; A second equivalent thermal conductivity determination unit is used to determine a second series thermal conductivity and a second parallel thermal conductivity of the secondary transposed Litz line along the width direction based on the second series thermal resistance model and the second parallel thermal resistance model, respectively, and take a weighted sum of the second series thermal conductivity and the second parallel thermal conductivity as a second equivalent thermal conductivity of the secondary transposed Litz line along the width direction; a third equivalent thermal conductivity determining unit, for determining a third series thermal conductivity and a third parallel thermal conductivity of the secondary transposition Litz line along the thickness direction, respectively, based on the third series thermal resistance model and the third parallel thermal resistance model, and taking a weighted sum of the third series thermal conductivity and the third parallel thermal conductivity as the third equivalent thermal conductivity of the secondary transposition Litz line along the thickness direction.

[0022] The beneficial effects of the present invention are as follows: the method for determining the equivalent thermal conductivity of the secondary transposed Litz line provided by the present invention respectively constructs a second series thermal resistance model, a second parallel thermal resistance model, a third series thermal resistance model and a third parallel thermal resistance model in the width and thickness directions of the secondary transposed Litz line, takes into account the two situations of series thermal diffusion and parallel thermal diffusion between different materials in the heat flow in the secondary transposed Litz line, takes into account the common influence of the two situations of series thermal diffusion and parallel thermal diffusion on the equivalent thermal conductivity, and improves the accuracy of the determined equivalent thermal conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 A schematic flow chart of an embodiment of a method for determining the equivalent thermal conductivity of a secondary transposed Litz line provided by the present invention; Figure 2 A schematic diagram of the structure of an embodiment of a secondary transposed Litz line provided by the present invention; Figure 3 A schematic diagram of the three-dimensional structure of the secondary transposed Litz line provided by the present invention; Figure 4 This is a schematic diagram of an embodiment of the process of determining the second series thermal conductivity in step S103 of the present invention; Figure 5(a) is a schematic structural diagram of an embodiment of an enameled round copper wire provided by the present invention; Figure 5 (b) is a schematic structural diagram of an embodiment of a model for dividing the thermal resistance of enameled round copper wires in series provided by the present invention; Figure 5 (c) is a schematic diagram of an embodiment of the present invention providing a series thermal resistance model of enameled round copper wires; Figure 6 (a) is a schematic structural diagram of an embodiment of a single-transposition Litz line provided by the present invention; Figure 6 (b) is a schematic diagram of an embodiment of the single-transposition Litz line series thermal resistance partitioning model provided by the present invention; Figure 6 (c) is a schematic structural diagram of an embodiment of the single-transposition Litz line series thermal resistance model provided by the present invention; Figure 7 A schematic structural diagram of an embodiment of a secondary transposed Litz line series thermal resistance partitioning model provided by the present invention; Figure 8 A schematic diagram of the structure of an embodiment of the two-transposed Litz line series thermal resistance model provided by the present invention; Fig. 9 A schematic diagram of an embodiment of determining the second parallel thermal conductivity in step S103 provided by the present invention; Fig.10 (a) is a schematic diagram of an embodiment of a parallel thermal resistance partition model of enameled round copper wires provided by the present invention; Fig.10 (b) is a schematic diagram of an embodiment of the parallel thermal resistance model of enameled round copper wires provided by the present invention; Fig.11 (a) is a schematic diagram of an embodiment of the single-transposition Litz line parallel thermal resistance partitioning model provided by the present invention; Fig.11 (b) is a schematic diagram of the structure of an embodiment of the single-transposition Litz line parallel thermal resistance model provided by the present invention; Fig.12 A schematic structural diagram of an embodiment of a secondary transposed Litz line parallel thermal resistance partitioning model provided by the present invention; Fig.13 A schematic diagram of the structure of an embodiment of the two-transposed Litz line parallel thermal resistance model provided by the present invention; Fig.14 A schematic diagram of the structure of an embodiment of determining the weighted weight of equivalent thermal conductivity provided by the present invention; Fig.15A schematic structural diagram of an embodiment of a device for determining equivalent thermal conductivity of a secondary transposed Litz line provided by the present invention. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0026] It should be understood that the schematic drawings are not drawn to scale. The flowchart used in the present invention shows the operations implemented according to some embodiments of the present invention. It should be understood that the operations of the flowchart can be implemented out of order, and the steps without logical context can be reversed in order or implemented simultaneously. In addition, those skilled in the art, under the guidance of the content of the present invention, can add one or more other operations to the flowchart, and can also remove one or more operations from the flowchart. Some of the block diagrams shown in the accompanying drawings are functional entities, which do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software form, or in one or more hardware modules or integrated circuits, or in different networks and / or processor systems and / or microcontroller systems.

[0027] Reference to an "embodiment" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0028] The present invention provides a method and device for determining the equivalent thermal conductivity of a secondary transposed Litz line, which are described below.

[0029] Figure 1 A schematic flow chart of an embodiment of a method for determining the equivalent thermal conductivity of a secondary transposed Litz line provided by the present invention is shown in FIG. Figure 1 As shown, the method for determining the equivalent thermal conductivity of the secondary transposed Litz line includes: S101, constructing a first parallel thermal resistance model along the length direction, a second series thermal resistance model and a second parallel thermal resistance model along the width direction, and a third series thermal resistance model and a third parallel thermal resistance model along the thickness direction of the secondary transposed Litz line; S102, determining a first equivalent thermal conductivity of the secondary transposed Litz line along the length direction based on a first parallel thermal resistance model; S103, determining a second series thermal conductivity and a second parallel thermal conductivity of the secondary transposed Litz line along the width direction based on the second series thermal resistance model and the second parallel thermal resistance model, respectively, and taking a weighted sum of the second series thermal conductivity and the second parallel thermal conductivity as a second equivalent thermal conductivity of the secondary transposed Litz line along the width direction; S104. Determine a third series thermal conductivity and a third parallel thermal conductivity of the secondary transposition Litz line along the thickness direction based on the third series thermal resistance model and the third parallel thermal resistance model, respectively, and take a weighted sum of the third series thermal conductivity and the third parallel thermal conductivity as a third equivalent thermal conductivity of the secondary transposition Litz line along the thickness direction.

[0030] In a specific embodiment of the present invention, Figure 2 As shown in Figure 1, the preparation process of the secondary transposed Litz line is: First, a copper round wire with a diameter of d (radius of r) is treated with an insulating paint film (with a double-sided thickness of t1mm) to obtain an enameled copper round wire with a diameter of d1; secondly, n1 enameled copper round wires with a diameter of d1 are transposed and vacuum pressure impregnated to obtain a wmm×bmm primary transposed Litz wire, and after vacuum pressure impregnation, the enameled copper round wire is attached with a resin layer with a double-sided thickness of t2mm; then, the wmm×bmm primary transposed Litz wire is wrapped with a first polyimide film with a double-sided thickness of t3mm; thirdly, n2 wmm×bmm primary transposed Litz wires are subjected to a secondary transposition to obtain a Wmm×Bmm secondary transposed Litz wire, and the secondary transposed Litz includes a resin layer with a double-sided thickness of t4mm; then, the secondary transposed Litz wire is wrapped with a second polyimide film with a double-sided thickness of t5mm, and finally, the secondary transposed Litz wire is vacuum pressure impregnated as a whole.

[0031] Among them, the length direction, width direction and thickness direction of the secondary transposed Litz line are as follows Figure 3 shown.

[0032] It should be noted that: in order to simplify the analysis, the enameled copper round wire is extruded into a square in the process of preparing the first transposition Litz wire, that is, the enameled copper round wire is approximately simplified to a square, and the length of the square is determined according to the principle of equal area. For example: when the radius of the copper round wire is r, the length of the simplified square is .

[0033] Since there is no heat diffusion between series and parallel in the length direction of the secondary transposed Litz line, its equivalent thermal conductivity along the length direction is derived according to the parallel model, which will not be elaborated here.

[0034] Compared with the prior art, the method for determining the equivalent thermal conductivity of the secondary transposed Litz line provided in the embodiment of the present invention respectively constructs a second series thermal resistance model, a second parallel thermal resistance model, a third series thermal resistance model and a third parallel thermal resistance model in the width and thickness directions of the secondary transposed Litz line, considers the two situations of series thermal diffusion and parallel thermal diffusion between different materials of the heat flow in the secondary transposed Litz line, takes into account the common influence of the two situations of series thermal diffusion and parallel thermal diffusion on the equivalent thermal conductivity, and improves the accuracy of the determined equivalent thermal conductivity.

[0035] It can be seen from the preparation process of the secondary transposition Litz wire that its preparation process is: copper round wire-primary transposition Litz wire-secondary transposition Litz wire. Therefore, in some embodiments of the present invention, the determination process of the equivalent thermal conductivity of the secondary transposition Litz wire is also carried out according to this process. Specifically, the second series thermal resistance model includes the enameled copper round wire series thermal resistance model of the enameled copper round wire, the primary transposition series thermal resistance model of the primary transposition Litz wire, and the secondary transposition series thermal resistance model of the transposition Litz wire; then Figure 4 As shown, determining the second series thermal conductivity of the secondary transposed Litz line along the width direction based on the second series thermal resistance model in step S103 includes: S401, determining the enameled series equivalent thermal resistance of the enameled round copper wire based on the enameled round copper wire series thermal resistance model, and determining the enameled round copper wire equivalent series thermal conductivity based on the enameled series equivalent thermal resistance and the size parameters of the enameled round copper wire; S402, determining the first transposition series equivalent thermal resistance of the first transposition Litz line based on the first transposition series thermal resistance model and the enameled series equivalent thermal resistance, and determining the first transposition equivalent series thermal conductivity based on the first transposition series equivalent thermal resistance and the size parameters of the first transposition Litz line; S403, determining the secondary transposition series equivalent thermal resistance of the secondary transposition Litz line based on the secondary transposition series thermal resistance model and the primary transposition series equivalent thermal resistance, and determining the second series thermal conductivity based on the secondary transposition series equivalent thermal resistance and the size parameters of the secondary transposition Litz line.

[0036] In a specific embodiment of the present invention, Figure 5 As shown in (a), the enameled copper round wire series thermal resistance partition model is constructed based on the copper round wire, insulating paint film and resin layer. Since this structure is symmetrical, half of it is taken for analysis. The thermal resistance network is as follows: Figure 5 As shown in (b), this structure is divided into three regions from left to right along the series direction. The first region includes the first thermal resistance R 1i , the first thermal resistance of the insulating paint film R 1p , Copper round wire thermal resistance R 1c , the first thermal resistance of the insulating paint film R 1p、Resin first thermal resistance R 1i , the second area includes the second thermal resistance R of the resin from top to bottom 2i , the second thermal resistance of the insulating paint film R 2p 、Resin second thermal resistance R 2i , the third region includes the third resin thermal resistance R 3i .

[0037] Based on the thermal resistance analysis of the above structure, we can get Figure 5 (c) Enameled copper round wire series thermal resistance model. Figure 5 (c) The enameled copper round wire series thermal resistance model can be used to obtain the enameled series equivalent thermal resistance for:

[0038] Then the equivalent series thermal conductivity of enameled round copper wire is for:

[0039] Where r is the radius of the round copper wire; t1 is the double-sided thickness of the insulating paint film; t2 is the double-sided thickness of the resin layer coated on the enameled round copper wire; dl It is the length of a single enameled round copper wire along the length direction.

[0040] In a specific embodiment of the present invention, a single-transposition Litz wire is prepared from 23 enameled round copper wires. The structure of the single-transposition Litz wire is as follows: Figure 6 As shown in (a), similarly, due to its symmetry, the general structure is analyzed, and its thermal resistance division model is as follows Figure 6 As shown in (b), this structure is divided into two regions from left to right along the series direction. The first region includes the fourth thermal resistor R 4n , Enameled round copper wire thermal resistance R 4c 、Polyimide fourth thermal resistance R 4n , the second region includes a fifth thermal resistance R of polyimide 5n .

[0041] Based on the thermal resistance analysis of the above structure, we can get Figure 6 (c) The single-transposition Litz line series thermal resistance model is based on Figure 6 (c) The single-transposition series thermal resistance model can be used to obtain the single-transposition series equivalent thermal resistance R q2 for:

[0042] Then the equivalent series thermal conductivity of one-time transposition is λ q2 for:

[0043] Wherein, w is the width of the first transposition Litz line; t3 is the double-sided thickness of the polyimide film coated with the first transposition Litz line.

[0044] In a specific embodiment of the present invention, Figure 7 It is the thermal resistance division model of the secondary transposition Litz wire, which consists of 9 primary transposition Litz wires and a coated resin layer. The thermal resistance network is divided into four areas from left to right along the series direction. The first area is the seventh thermal resistance R of polyimide. 7n , the second area includes the seventh resin thermal resistance R in parallel from top to bottom 7p The equivalent thermal resistance R of the seventh first-order series transposition 7c 、Four sixth-order transposition series equivalent thermal resistance R 6c And the eighth thermal resistance of polyimide R 8n , the third area includes the eighth resin thermal resistance R in parallel from top to bottom 8p And the eighth first transposition series equivalent thermal resistance R 8c 、Four sixth-order transposition series equivalent thermal resistance R 6c And the eighth thermal resistance of polyimide R 8n , the fourth area is the seventh thermal resistance of polyimide R 7n .

[0045] Based on the above thermal resistance structure, we can get Figure 8 The secondary transposed Litz line series thermal resistance model is based on Figure 8 The secondary transposition series thermal resistance model can be obtained by R eq2 for:

[0046] Then the second series thermal conductivity is:

[0047] In the formula, is the second series thermal conductivity.

[0048] Similarly, the second parallel thermal resistance model includes the parallel thermal resistance model of the enameled copper round wire, the first transposition parallel thermal resistance model of the first transposition Litz wire, and the second transposition parallel thermal resistance model of the transposition Litz wire; then Fig. 9 As shown, determining the second parallel thermal conductivity of the secondary transposed Litz line along the width direction based on the second parallel thermal resistance model in step S103 includes: S901. Determine the enameled parallel equivalent thermal resistance of the enameled round copper wire based on the enameled round copper wire parallel thermal resistance model, and determine the enameled round copper wire equivalent parallel thermal conductivity based on the enameled parallel equivalent thermal resistance and the size parameters of the enameled round copper wire; S902, determining the first-transposition parallel equivalent thermal resistance of the first-transposition Litz wire based on the first-transposition parallel thermal resistance model and the equivalent parallel thermal conductivity of the enameled copper round wire, and determining the first-transposition equivalent parallel thermal conductivity based on the first-transposition parallel equivalent thermal resistance and the size parameters of the first-transposition Litz wire; S903, determining the secondary transposition parallel equivalent thermal resistance of the secondary transposition Litz line based on the secondary transposition parallel thermal resistance model and the primary transposition series equivalent thermal resistance, and determining the second parallel thermal conductivity based on the secondary transposition parallel equivalent thermal resistance and the size parameters of the secondary transposition Litz line.

[0049] In a specific embodiment of the present invention, the parallel thermal resistance division model of the enameled round copper wire is as follows: Fig.10 As shown in (a), it is divided into five areas from top to bottom along the parallel direction. The first area is the third parallel resin thermal resistance , the second region includes the second parallel film thermal resistance in series and the second parallel resin thermal resistance , the third area includes the first parallel copper round wire thermal resistance in series , Thermal resistance of the first parallel paint film and the first parallel resin thermal resistance , the fourth region includes the second parallel film thermal resistance in series and the second parallel resin thermal resistance , the fifth area is the third parallel resin thermal resistance .

[0050] Based on the above thermal resistance analysis, we can get Fig.10 (b) The parallel thermal resistance model of enameled copper round wire. Based on this parallel thermal resistance model of enameled copper round wire, the equivalent parallel thermal conductivity of enameled copper round wire can be obtained. R e2 0 for:

[0051] Then the equivalent series thermal conductivity of enameled round copper wire is λ e2 0 for:

[0052] In a specific embodiment of the present invention, a single transposition Litz wire is prepared from 23 enameled round copper wires, and its thermal resistance network is as follows: Fig.11 As shown in (a), this structure is divided into three regions from top to bottom along the parallel direction. The first region is the fourth thermal resistor of the polyimide parallel connection. , the second area includes the parallel enameled copper round wire thermal resistance connected in series from left to right And polyimide parallel fourth thermal resistance , the third area is the fourth thermal resistance of polyimide in parallel .

[0053] Based on the thermal resistance analysis of the above structure, we can get Fig.11 (b) The single-transposition Litz line series thermal resistance model is based on Fig.11 (b) The single-transposition series thermal resistance model can be used to obtain the single-transposition parallel equivalent thermal resistance R q2 0 for:

[0054] Then the equivalent thermal conductivity of the parallel connection is λ q2 0 for:

[0055] In a specific embodiment of the present invention, Fig.12 It is a parallel thermal resistance network of secondary transposition Litz wires, which is composed of 9 primary transposition Litz wires. The parallel thermal resistance network is divided into seven areas from top to bottom along the parallel direction. The first area is the eighth thermal resistance of parallel polyimide , the second region includes the seventh thermal resistor of the parallel polyimide in series from left to right , parallel seventh resin thermal resistance , parallel sixth first transposition series equivalent thermal resistance , parallel eighth resin thermal resistance And parallel polyimide seventh thermal resistance The third region, the fourth region, the fifth region and the sixth region all include a seventh thermal resistor of a parallel polyimide , two parallel sixth-order transposition series equivalent thermal resistance And parallel polyimide seventh thermal resistance , the seventh area is the eighth thermal resistance of parallel polyimide .

[0056] Based on the above thermal resistance structure, we can get Fig.13 The single-transposition Litz line parallel thermal resistance model is based on Fig.13 The secondary transposition parallel thermal resistance model can be obtained by R eq2 for:

[0057] Then the second parallel thermal conductivity is:

[0058] in, is the second parallel thermal conductivity.

[0059] It should be understood that the derivation process of the third series thermal conductivity and the third parallel thermal conductivity is the same as the derivation process of the second series thermal conductivity and the second parallel thermal conductivity, and will not be elaborated here.

[0060] Since the second equivalent thermal conductivity in the embodiment of the present invention is the weighted sum of the second series thermal conductivity and the second parallel thermal conductivity, and the third equivalent thermal conductivity is the weighted sum of the third series thermal conductivity and the third parallel thermal conductivity, that is, the weight distribution is crucial to the accuracy of the equivalent thermal conductivity. Therefore, in some embodiments of the present invention, Fig.14 As shown, the method for determining the equivalent thermal conductivity of the secondary transposed Litz line also includes: S1401, obtaining the diameter of the round copper wire and the film thickness of the insulating paint film; S1402, determining a volume fraction of the copper round wire based on the diameter and the paint film thickness, and determining a first weight of the second series thermal conductivity and a second weight of the third series thermal conductivity based on the volume fraction; S1403. Determine a second equivalent thermal conductivity and a third equivalent thermal conductivity based on the first weight, the second weight, the second series thermal conductivity, the second parallel thermal conductivity, the third series thermal conductivity, and the third parallel thermal conductivity.

[0061] Specifically, the second equivalent thermal conductivity is:

[0062]

[0063] In the formula, is the second equivalent thermal conductivity; is the first weight; V m is the volume fraction of copper round wire.

[0064] The third equivalent thermal conductivity is:

[0065]

[0066] In the formula, is the second equivalent thermal conductivity; is the second weight.

[0067] The embodiment of the present invention can further improve the accuracy of the determined equivalent thermal conductivity by assigning different series-parallel weights to the width and thickness directions of the secondary transposed Litz line.

[0068] Specifically, it has been verified through experiments that the relative error between the equivalent thermal conductivity determined by the traditional method and the test value is 6%, while the relative error between the equivalent thermal conductivity determined by the method proposed in the embodiment of the present invention and the test value is within 3.12%, and the accuracy is improved by 1.9 times.

[0069] In order to better implement the method for determining the equivalent thermal conductivity of the secondary transposed Litz wire in the embodiment of the present invention, based on the method for determining the equivalent thermal conductivity of the secondary transposed Litz wire, the embodiment of the present invention also provides a device for determining the equivalent thermal conductivity of the secondary transposed Litz wire, such as Figure 5 As shown, the equivalent thermal conductivity determination device 1500 of the secondary transposed Litz line includes: A series-parallel thermal resistance model construction unit 1501 is used to construct a first parallel thermal resistance model along the length direction, a second series thermal resistance model and a second parallel thermal resistance model along the width direction, and a third series thermal resistance model and a third parallel thermal resistance model along the thickness direction of the secondary transposed Litz line; A first equivalent thermal conductivity determining unit 1502 is used to determine a first equivalent thermal conductivity of a secondary transposed Litz line along a length direction based on a first parallel thermal resistance model; A second equivalent thermal conductivity determination unit 1503 is used to determine a second series thermal conductivity and a second parallel thermal conductivity of the secondary transposed Litz line along the width direction based on a second series thermal resistance model and a second parallel thermal resistance model, respectively, and take a weighted sum of the second series thermal conductivity and the second parallel thermal conductivity as a second equivalent thermal conductivity of the secondary transposed Litz line along the width direction; The third equivalent thermal conductivity determining unit 1504 is used to determine the third series thermal conductivity and the third parallel thermal conductivity of the secondary transposition Litz line along the thickness direction based on the third series thermal resistance model and the third parallel thermal resistance model, respectively, and take the weighted sum of the third series thermal conductivity and the third parallel thermal conductivity as the third equivalent thermal conductivity of the secondary transposition Litz line along the thickness direction.

[0070] The device 1500 for determining the equivalent thermal conductivity of a secondary transposed Litz wire provided in the above embodiment can implement the technical solution described in the above embodiment of the method for determining the equivalent thermal conductivity of a secondary transposed Litz wire. The specific implementation principles of the above modules or units can refer to the corresponding contents in the above embodiment of the method for determining the equivalent thermal conductivity of a secondary transposed Litz wire, which will not be repeated here.

[0071] Those skilled in the art will appreciate that all or part of the processes of the above-mentioned embodiments can be implemented by instructing related hardware (such as a processor, a controller, etc.) through a computer program, and the computer program can be stored in a computer-readable storage medium, wherein the computer-readable storage medium is a disk, an optical disk, a read-only storage memory, or a random access memory, etc.

[0072] The above is a detailed introduction to a method and device for determining the equivalent thermal conductivity of a secondary transposed Litz wire provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for determining the equivalent thermal conductivity of a secondary transposed Litz line, characterized in that: include: Constructing a first parallel thermal resistance model along the length direction, a second series thermal resistance model and a second parallel thermal resistance model along the width direction, and a third series thermal resistance model and a third parallel thermal resistance model along the thickness direction of the secondary transposed Litz line; Determine a first equivalent thermal conductivity of the secondary transposed Litz line along the length direction based on the first parallel thermal resistance model; Determine the second series thermal conductivity and the second parallel thermal conductivity of the secondary transposed Litz line along the width direction based on the second series thermal resistance model and the second parallel thermal resistance model, and use the weighted sum of the second series thermal conductivity and the second parallel thermal conductivity as the second equivalent thermal conductivity of the secondary transposed Litz line along the width direction; A third series thermal conductivity and a third parallel thermal conductivity of the secondary transposition Litz line along the thickness direction are determined based on the third series thermal resistance model and the third parallel thermal resistance model, respectively, and a weighted sum of the third series thermal conductivity and the third parallel thermal conductivity is used as the third equivalent thermal conductivity of the secondary transposition Litz line along the thickness direction.

2. The method for determining the equivalent thermal conductivity of the secondary transposed Litz line according to claim 1, characterized in that: The preparation process of the secondary transposed Litz line is as follows: Treating the round copper wire with an insulating paint film to obtain an enameled round copper wire; Transposing a plurality of enameled round copper wires, performing vacuum pressure impregnation on the transposed plurality of enameled round copper wires to obtain a primary transposed Litz wire, and wrapping a first polyimide film around the primary transposed Litz wire; The first transposed Litz wire wrapped with the first polyimide film is subjected to a second transposition to obtain a second transposed Litz wire, a second polyimide film is wrapped around the second transposed Litz wire, and the second transposed Litz wire wrapped with the second polyimide film is subjected to vacuum pressure impregnation.

3. The method for determining the equivalent thermal conductivity of the secondary transposed Litz line according to claim 2, characterized in that: The second series thermal resistance model includes the enameled copper round wire series thermal resistance model of the enameled copper round wire, the first transposition series thermal resistance model of the first transposition Litz wire, and the second transposition series thermal resistance model of the transposition Litz wire; determining the second series thermal conductivity of the second transposition Litz wire along the width direction based on the second series thermal resistance model includes: Determine the enameled series equivalent thermal resistance of the enameled round copper wire based on the enameled round copper wire series thermal resistance model, and determine the enameled round copper wire equivalent series thermal conductivity based on the enameled series equivalent thermal resistance and the size parameters of the enameled round copper wire; Determine the first transposition series equivalent thermal resistance of the first transposition Litz wire based on the first transposition series thermal resistance model and the equivalent series thermal conductivity of the enameled copper round wire, and determine the first transposition equivalent series thermal conductivity based on the first transposition series equivalent thermal resistance and the size parameters of the first transposition Litz wire; The secondary transposition series equivalent thermal resistance of the secondary transposition Litz line is determined based on the secondary transposition series thermal resistance model and the primary transposition series equivalent thermal resistance, and the second series thermal conductivity is determined based on the secondary transposition series equivalent thermal resistance and the size parameters of the secondary transposition Litz line.

4. The method for determining the equivalent thermal conductivity of the secondary transposed Litz line according to claim 3, characterized in that: The second series thermal conductivity is: In the formula, is the second series thermal conductivity; is the equivalent thermal resistance of the secondary transposition series connection; w is the width of a transposed Litz line; b is the thickness of the Litz line of a transposition; t 3 is the double-sided thickness of the first polyimide film; t 4 is the bilateral thickness of the resin layer in the secondary transposition Litz line; t 5 is the double-sided thickness of the second polyimide film; dl It is the length of a single enameled round copper wire along the length direction.

5. The method for determining the equivalent thermal conductivity of the secondary transposed Litz line according to claim 4, characterized in that: The second parallel thermal resistance model includes the enameled copper round wire parallel thermal resistance model of the enameled copper round wire, the first transposition parallel thermal resistance model of the first transposition Litz wire, and the second transposition parallel thermal resistance model of the transposition Litz wire; then determining the second parallel thermal conductivity of the second transposition Litz wire along the width direction based on the second parallel thermal resistance model includes: Determine the enameled parallel equivalent thermal resistance of the enameled round copper wire based on the enameled parallel thermal resistance model of the enameled round copper wire, and determine the enameled parallel equivalent thermal conductivity of the enameled round copper wire based on the enameled parallel equivalent thermal resistance and the size parameters of the enameled round copper wire; Determine the first-transposition parallel equivalent thermal resistance of the first-transposition Litz wire based on the first-transposition parallel thermal resistance model and the equivalent parallel thermal conductivity of the enameled copper round wire, and determine the first-transposition equivalent parallel thermal conductivity based on the first-transposition parallel equivalent thermal resistance and the size parameters of the first-transposition Litz wire; The secondary transposition parallel equivalent thermal resistance of the secondary transposition Litz line is determined based on the secondary transposition parallel thermal resistance model and the primary transposition series equivalent thermal resistance, and the second parallel thermal conductivity is determined based on the secondary transposition parallel equivalent thermal resistance and the size parameters of the secondary transposition Litz line.

6. The method for determining the equivalent thermal conductivity of the secondary transposed Litz line according to claim 5, characterized in that: The second parallel thermal conductivity is: In the formula, is the second parallel thermal conductivity; is the secondary transposition parallel equivalent thermal resistance; w is the width of a transposed Litz line; b is the thickness of the Litz line of a transposition; t 3 is the double-sided thickness of the first polyimide film; t 4 is the bilateral thickness of the resin layer in the secondary transposition Litz line; t 5 is the thickness of the second polyimide film; dl It is the length of a single enameled round copper wire along the length direction.

7. The method for determining the equivalent thermal conductivity of a secondary transposed Litz line according to claim 6, characterized in that: The method further comprises: Obtaining the diameter of the round copper wire and the film thickness of the insulating paint film; Determining a volume fraction of the copper round wire based on the diameter and the paint film thickness, and determining a first weight of the second series thermal conductivity and a second weight of the third series thermal conductivity based on the volume fraction; The second equivalent thermal conductivity and the third equivalent thermal conductivity are determined based on the first weight, the second weight, the second series thermal conductivity, the second parallel thermal conductivity, the third series thermal conductivity, and the third parallel thermal conductivity.

8. The method for determining the equivalent thermal conductivity of a secondary transposed Litz line according to claim 7, characterized in that: The second equivalent thermal conductivity is: In the formula, is the second equivalent thermal conductivity; is the first weight; V m is the volume fraction of copper round wire.

9. The method for determining the equivalent thermal conductivity of a secondary transposed Litz line according to claim 7, characterized in that: The third equivalent thermal conductivity is: In the formula, is the second equivalent thermal conductivity; is the second weight; V m is the volume fraction of copper round wire.

10. A device for determining the equivalent thermal conductivity of a secondary transposed Litz line, characterized in that: include: A series-parallel thermal resistance model construction unit, used to construct a first parallel thermal resistance model along the length direction, a second series thermal resistance model and a second parallel thermal resistance model along the width direction, and a third series thermal resistance model and a third parallel thermal resistance model along the thickness direction of the secondary transposed Litz line; A first equivalent thermal conductivity determination unit, configured to determine a first equivalent thermal conductivity of the secondary transposed Litz line along a length direction based on the first parallel thermal resistance model; A second equivalent thermal conductivity determination unit is used to determine a second series thermal conductivity and a second parallel thermal conductivity of the secondary transposed Litz line along the width direction based on the second series thermal resistance model and the second parallel thermal resistance model, respectively, and take a weighted sum of the second series thermal conductivity and the second parallel thermal conductivity as a second equivalent thermal conductivity of the secondary transposed Litz line along the width direction; a third equivalent thermal conductivity determining unit, for determining a third series thermal conductivity and a third parallel thermal conductivity of the secondary transposition Litz line along the thickness direction, respectively, based on the third series thermal resistance model and the third parallel thermal resistance model, and taking a weighted sum of the third series thermal conductivity and the third parallel thermal conductivity as the third equivalent thermal conductivity of the secondary transposition Litz line along the thickness direction.

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